Wireless communication systems, such as cellular telephone systems, have proved to be very popular. Such systems typically include numerous mobile units (e.g., cellular telephones), a plurality of base stations at fixed locations, and one or more switching centers connecting the wireless communication systems to other communications systems, such as the land line public switched telephone network.
Typically, the mobile units are transportable and designed to function in a variety of ambient acoustic environments. For instance, the mobile units may be designed to function in an office environment or inside a moving vehicle. In addition, various types of hands free adapters have been developed that allow mobile units to operate without being held next to a person's head. Hands free adapters typically include a means for holding the mobile unit, a speaker, a microphone, and associated electronics for amplification. When the mobile unit is coupled to the hands free adapter, any speakers or microphones in the mobile unit are typically disabled and the hands free adapter's speaker and microphone are used instead. Hands free adapters may also contain other electronics such as battery charging circuits.
When a mobile unit is used in conjunction with a hands free adapter, the acoustic environment is different than when the mobile unit is held next to a person's head. For instance, the distance between the microphone and the person's mouth will be longer, as will the distance from the speaker to the person's ear. These longer distances mean that acoustic attenuation plays a larger role in getting the acoustic signals to and from the user. In addition, there is greater chance for undesirable interference from ambient acoustic noise. Further, hands free configurations may allow for an acoustic echo path to be created between the speaker and the microphone.
Typically, modern mobile units are equipped with hands free circuits to adjust for the different acoustic environments encountered when the mobile units are used with hands free adapters. However, many mobile units are designed for optimum performance in one particular environment and are unable to optimally adjust for different ambient acoustic environments. That is, a hands free circuit in the mobile unit may be designed to handle a noisy vehicle-in-motion environment by increasing the audio gain for the speaker and reducing the audio gain for the microphone. However, these adjustments may not be optimum when the mobile unit/hands free adapter combination is in a quieter office environment where a more optimum setting may include decreasing audio gain for the speaker and increasing audio gain for the microphone. Thus, one setting for hands free operation may not be suitable for all ambient acoustic environments.
Most hands free adapters contain circuits which adjust the audio gains for the speaker and the microphone by a fixed predetermined amount. A plurality of hands free adapters may be used, one designed for each ambient acoustic environment, but this increases cost and requires greater user effort.
As such, there is a need for a device for use with wireless communications mobile units that can sense the ambient acoustic environment and adjust the audio characteristics to one of a plurality of different available settings such that the audio characteristics are more optimally adjusted for the actual ambient acoustic environment encountered.